The invention relates to a displaceable clamping element.
In particular, the invention relates to an adjustable clamping element for top tools on presses, the housing member of which is held suspended with a T-shaped profiled head in a T-slot arranged horizontally on the underside of a press ram and displaceable in said slot, said element having clamping means for the top tool and contact members for the top tool for determining the clamping position.
The holding and guiding of movable clamping elements for tools and, in particular, workpieces, in T-slot guides in the holding part are very common. This system of clamping is used also in the case of tools which are to be clamped suspended from rams of presses, in particular also in the case of transfer presses. The clamping forces are exerted by hydraulically actuated clamping pistons or else mechanically, for instance by toggle levers. For the horizontal displacement of the clamping elements, several of which are generally used for the clamping of a tool, spindle drives having a motor-driven spindle which passes through a spindle nut in the clamping element are known, as well as chain drives or motion drives consisting of piston-cylinder units.
In the case of suspended clamping elements, play is present between the housing member of the clamping element and the press ram in unloaded condition, for instance also upon displacement for adaptation to different tool diameters and corresponding adjustment to new clamping positions for the clamping element, which play results from the guidance play necessary for the displacement movement and the tolerances of the T-slot guide and becomes visible due to the weight of the clamping element. This play, without which displacement of the clamping element is not possible, leads, under load by the clamping forces of the clamping elements, to a sudden canting of the housing member with respect to the press ram in the clamping position. This canting during the clamping takes place suddenly with very great force, so that damage can frequently be observed due to the partially increased pressure per unit of surface between the housing member of the clamping element and the press ram, particularly if the displacement drive used requires smoothly machined slide surfaces in the T-slot guide as well as on the profiled head of the housing member and also in the T-slot of the press ram.